Physics Essentials
What is a simple pendulum?
Gravitational potential energy is PE = m g h , energy due to position in a gravitational field. h is height above reference level.
Newton's law of universal gravitation: Every particle attracts every other with force F = G m1 m2 / r² , where G is the gravitational constant, directed along the line joining centers.
The base SI units are the metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.
A simple pendulum approximates simple harmonic motion (SHM) for small angles, period T = 2π √(L / g) independent of mass.
Physics Essentials
What are the base SI units?
The base SI units are the metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.
The First Law states energy conservation: ΔU = Q - W , change in internal energy equals heat added minus work done by system.
Ideal gas law: PV = n R T , relates pressure, volume, moles, temperature. R universal gas constant.
In uniform circular motion, speed is constant but velocity changes direction, requiring centripetal acceleration a_c = v² / r towards center, provided by centripetal force.
Physics Essentials
State the three equations of motion for constant acceleration.
Magnetic field B
Mass is the amount of matter in an object, measured in kg, invariant. Weight is the gravitational force on mass, W = mg , varying with location.
Friction is the force opposing relative motion between surfaces in contact. Static friction prevents motion; kinetic friction acts during sliding, both proportional to normal force.
The equations are: v = u + at , s = ut + (1/2)at² , and v² = u² + 2as , where u is initial velocity, v final velocity, a acceleration, s displacement, t time.
Physics Essentials
What is the Doppler effect?
Doppler effect: Observed frequency shifts due to relative motion between source and observer. f' = f (v ± vo) / (v ± vs) .
The equations are: v = u + at , s = ut + (1/2)at² , and v² = u² + 2as , where u is initial velocity, v final velocity, a acceleration, s displacement, t time.
Refraction: Bending of light at interface due to speed change. Snell's law: n1 sinθ1 = n2 sinθ2 , n refractive index.
Distance is the total path length traveled, a scalar, while displacement is the straight-line vector from initial to final position. Displacement can be zero even if distance is not, as in a closed loop.
Physics Essentials
What is acceleration?
Acceleration is the rate of change of velocity with time, a vector quantity. It can be positive, negative (deceleration), or change direction, calculated as a = Δv / Δt .
Mass is the amount of matter in an object, measured in kg, invariant. Weight is the gravitational force on mass, W = mg , varying with location.
In the absence of non-conservative forces like friction, total mechanical energy (KE + PE) is conserved. Energy converts between forms but sum remains constant.
Torque is the rotational equivalent of force: τ = r F sinθ , causing angular acceleration. Measured in N·m.
Physics Essentials
State Archimedes' principle.
Mass is the amount of matter in an object, measured in kg, invariant. Weight is the gravitational force on mass, W = mg , varying with location.
Transverse waves have oscillations perpendicular to propagation (e.g., light); longitudinal have parallel (e.g., sound). Both obey v = f λ .
Archimedes' principle: Buoyant force equals weight of displaced fluid. Objects float if buoyant force ≥ weight.
Acceleration is the rate of change of velocity with time, a vector quantity. It can be positive, negative (deceleration), or change direction, calculated as a = Δv / Δt .
Physics Essentials
What is pressure in fluids?
In series, current same, voltages add, total R = sum Ri. In parallel, voltage same, currents add, 1/R_total = sum 1/Ri.
Pressure is force per unit area: P = F / A . In fluids, it acts equally in all directions.
Friction is the force opposing relative motion between surfaces in contact. Static friction prevents motion; kinetic friction acts during sliding, both proportional to normal force.
The Zeroth Law: If two systems are in thermal equilibrium with a third, they are in equilibrium with each other, defining temperature.
Physics Essentials
What is friction?
Archimedes' principle: Buoyant force equals weight of displaced fluid. Objects float if buoyant force ≥ weight.
Friction is the force opposing relative motion between surfaces in contact. Static friction prevents motion; kinetic friction acts during sliding, both proportional to normal force.
The equations are: v = u + at , s = ut + (1/2)at² , and v² = u² + 2as , where u is initial velocity, v final velocity, a acceleration, s displacement, t time.
Coulomb's law: Force between charges F = k q1 q2 / r² , k = 9×10^9 N·m²/C², attractive if opposite signs.
Physics Essentials
What is power?
The Zeroth Law: If two systems are in thermal equilibrium with a third, they are in equilibrium with each other, defining temperature.
The base SI units are the metre (m) for length, kilogram (kg) for mass, second (s) for time, ampere (A) for electric current, kelvin (K) for temperature, mole (mol) for amount of substance, and candela (cd) for luminous intensity.
Power is the rate of doing work or transferring energy: P = W / t or P = F v . Measured in watts (W), where 1 W = 1 J/s.
Speed is the scalar rate of change of distance with time, while velocity is the vector rate of change of displacement with time. Average speed is total distance over time; average velocity is displacement over time.